[dpdk-stable] [PATCH][V2] net/af_xdp: avoid deadlock due to empty fill queue

[Li RongQing]

when receive packets, it is possible to fail to reserve
fill queue, since buffer ring is shared between tx and rx,
and maybe not available temporary. at last, both fill
queue and rx queue are empty.

then kernel side will be unable to receive packets due to
empty fill queue, and dpdk will be unable to reserve fill
queue because dpdk has not pakcets to receive, at last
deadlock will happen

so move reserve fill queue before xsk_ring_cons__peek
to fix it

Acked-by: Ciara Loftus <ciara.loftus at intel.com>
Signed-off-by: Li RongQing <lirongqing at baidu.com>
Signed-off-by: Dongsheng Rong <rongdongsheng at baidu.com>
Cc: stable at dpdk.org
---
diff with v1: 

cc stable at dpdk.org
change af_xdp: as net/af_xdp

 drivers/net/af_xdp/rte_eth_af_xdp.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
index 7ce4ad04a..2dc9cab27 100644
--- a/drivers/net/af_xdp/rte_eth_af_xdp.c
+++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
@@ -304,6 +304,10 @@ af_xdp_rx_cp(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	uint32_t free_thresh = fq->size >> 1;
 	struct rte_mbuf *mbufs[ETH_AF_XDP_RX_BATCH_SIZE];
 
+	if (xsk_prod_nb_free(fq, free_thresh) >= free_thresh)
+		(void)reserve_fill_queue(umem, ETH_AF_XDP_RX_BATCH_SIZE, NULL);
+
+
 	if (unlikely(rte_pktmbuf_alloc_bulk(rxq->mb_pool, mbufs, nb_pkts) != 0))
 		return 0;
 
@@ -317,9 +321,6 @@ af_xdp_rx_cp(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 		goto out;
 	}
 
-	if (xsk_prod_nb_free(fq, free_thresh) >= free_thresh)
-		(void)reserve_fill_queue(umem, ETH_AF_XDP_RX_BATCH_SIZE, NULL);
-
 	for (i = 0; i < rcvd; i++) {
 		const struct xdp_desc *desc;
 		uint64_t addr;
-- 
2.16.2